Dear Sri Jaganathan :
SravaNa DvAdasi comes once a year and this
Isvara Year , it falls on Sunday , 14th of September
( Sukla Paksha DvAdasi ) . The ruling by the saasthrAs is
that the upavAsam on Sukla Paksha SravaNa DvAdasi
is equal to the accumulated merits of fasting on 10,000
Ekadasis . Thus , Sukla Paksha SravaNa DvAdasi is
even more sacred than KrishNa paksha SravaNa
DvAdasi .
The source for the NirNayam of Tithi and UpavAsam
come from many PurANAs and SamhitAs as well as
Sroutha SutrAs .
These nirNaya granthAs rule that the upavAsam should
be done on SravaNa DvAdasi and the paaraNai
( breaking of the fast ) on TrayOdasi .
These aadhAra granthAs point out also that one can safely
skip the fasting on the Ekadasi day prior to SravaNa dvAdasi
and should fast on the SravaNa dvAdasi day , if one is unable to
fast on both the days . VishNu purANam has also ruled that
one , who is unable to fast on SravaNa dvAdasi day should limit
oneself to fruits, milk and roots and stay away from salt
( lavaNa Varjitham and no rice as you pointed out ) .Such a person
will still get the fruits of this special upavAsam , which is
suggested to remove mahA paathakams such as
Brahma hatthi dhosham .
The sacredness of the SravaNa dvAdasi upavAsam is
pointed out in another way . SruthisAra Samucchayam states
that the puNyam accumulated over five previous years
are destroyed by nonobservance of this fast by a
Sri VaishNavA .
To be at Oppiliappan Sannadhi on SravaNa DvAdasi day
and have the darsanam of SravaNa dheepam is one of the
gretest of blessings that one can have . I guess the acceptable
alternative for us " locked up " here is the recitation of
Sri VishNu Sahasra Naamam in front of a dheepam .
Thanks very much for reminding us all about this important day .
V.Sadagopan